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rise to females. First and second polar bodies are formed and the first 
divides thus same whether the nucleus consists of tne female pronucleus 
only or of the female and male pronuclei fused. Unlike the eggs of 
monembryonic species the cleavage nuclei here become separated from 
one another by cell walls and the ‘nucleolo’ from the very beginning 
is segregated at each division in a single cleavage cell. This cell 
divides more slowly than the others; the ‘nucleolo’ gradually becomes 
vacuolated, breaks down, and finally is evenly scattered throughout 
the entire cytoplasm. Just before the sixteen-cell stage is reached 
the cell containing the disintegrated ‘nucleolo’ divides and the two 
daughter cells are provided with equal amounts of its substance. 
SILVESTRI was only able to trace the cells containing the remains of the 
‘nucleolo’ until four of these were present. Nevertheless, he concludes 
that these and these alone give rise to the germ cells. This con- 
clusion seems well founded when the history of this ‘nucleolo’ is 
compared with that of similar bodies (keimbahn-determinants) in the 
eggs of certain other animals. 
Two regions develop in the eggs of these polyembryonic Hymen- 
optera, (1) an anterior or polar region containing the polar bodies 
and (2) the posterior embryonic region. This latter again becomes 
differentiated into two regions, (1) and anterior ‘massa germinigera’ 
which gives rise to normal larvae, and (2) a posterior ‘massa mon- 
embrionale’ which produces the so-called asexual larvae. These lack 
reproductive, respiratory, circulatory, and excretory systems. They 
are supposed to develop from cell masses which do not contain 
descendants of the cell with ‘nucleolar’ material, and to serve the 
purpose of tearing apart the organs of the host thus making them 
available as food for the normal larvae. The ‘ massa monembrionale,’ 
according to this view, consists entirely of somatic cells, whereas the 
‘massa germinigera’ possesses both somatic and germ cells. Doubts 
have been expressed regarding the development of the asexual and 
SILVESTRI'S results need confirmation. 
The present paper is the outcome of an attempt to trace the 
origin of the ‘nucleolo’ of Sınvesmeı. There seems to be no doubt 
that this body is a keimbahn-determinant in both monembryonie and 
polyembryonic Hymenoptera. Its identification as the nucleolus from 
the oöcyte nucleus by Sırvzsırı did not seem to the writer to be at 
all certain. This together with its apparent conspicuousness led to 
the investigation the results of which are reported in this contribution. 
